He was touted as the man who could be the first black president before Barack Obama beat him to it.

Despite never running in a statewide election before, he’s been embraced by some of America’s biggest names, including Oprah Winfrey.

Now, Cory Booker must prove he’s been worthy all of the hype. After years of preparing for a career beyond Newark, Booker formally announced his candidacy for the U.S. Senate over the weekend. He enters the race as a heavy favorite, with polls showing him with a 40-point lead over two U.S. House members who are also expected to run in a Democratic primary against Booker.

And the primary winner will be the overwhelming favorite in October in New Jersey, a reliably blue state in federal elections.

But the next few months are still very important for Booker. With such a strong lead, a defeat in the August Democratic primary or November election would likely end the Newark mayor’s political career.

He has already irritated Democrats nationally by openly criticizing the strategy of President Obama’s campaign last year and Democrats in his home state by running for a U.S. Senate that Democrats already hold instead of taking on the challenge of running against popular New Jersey Gov. Chris Christie, a Republican.

More importantly, while he has never formally said so, Booker, like Massachusetts Sen. Elizabeth Warren and a few other prominent Democrats, is widely believed to be a potential candidate for the Democratic presidential nomination in the future. (With Hillary Clinton or Joe Biden likely to run in 2016, a new generation of Democrats will likely opt for campaigns in 2020 or 2024.) This Senate campaign is Booker’s first formal foray into the national political scene and will be closely watched, in part because there are only a handful of major elections in 2013.

In the next few months, Booker can reverse the impression of some political elites that he is more focused on his brand than governing, as the New York Timessuggested in a story last year that damaged the mayor’s reputation. The campaign could also illustrate if Booker will eventually get the strong, united support of African-Americans that was a major factor in Obama’s rise, or if the at times lukewarm comments from black leaders in Newark about their mayor reflect a broader wariness about him.

This six-month sprint is not the campaign Booker expected. With an election in November 2014, Booker planned to spend much of the next year building stronger alliances around the state and recasting himself from a man known for his massive Twitter following and television appearances to a candidate intensely focused on New Jersey.

Now, Booker must run sooner and in a stronger field than he anticipated. Democrats Rush Holt and Frank Pallone, who have long wanted a promotion, can now run against Booker, knowing if they lose than can just return to their House seats.